Many critically ill patients survive their initial episode of acute illness but go on to develop persistent organ failures necessitating prolonged life support, a syndrome known as chronic critical illness. Increasingly, patients with chronic critical illness receive care in long---termacute care hospitals (LTACs), specialized facilities for the care of these high---risk, high---cost patients. In our prior work we demonstrated that LTACs play an important role in the care of chronic critical illness, producing similar outcomes at lower costs compared to traditional intensive care units (ICUs). Yet our work also demonstrated wide variation in survival across LTACs, with significant differences in long---term mortality that are not explained by differences in case---mix. This work affirmed the essential position of LTACs in the US health system, but also highlighted a pressing need for research on how to best organize and manage care within LTACs in order to optimize care for patients with chronic critical illness. Analogous care settings such as ICUs and nursing homes have a rich evidence base informing their organization and management, but to date no such data exist for LTACs. In this project we will address this fundamental knowledge gap by identifying the key clinical and organizational factors associated with LTAC performance. Our central hypothesis is that objective clinical and organizational factors will distinguish high performing LTACs from low performing ones. Building off a novel hierarchical risk---adjustment model for measuring LTAC---specific mortality, we will first perform site visits at five US LTACs with the lowest risk---adjusted mortality and five LTACs with highest risk--- adjusted mortality. During these site visits we will conduct in---depth ethnography and semi---structured interviews to identify the clinical and organizational factors associated with positive outcomes. Second, we will develop and field a quantitative survey of physician and nurse managers at all US LTACs, linking the survey back to patient---level outcomes data and empirically defining LTAC clinical and organizational best practices. By shifting the paradigm of LTAC evaluation away from whether they work to how and where they work best, this project will be the first rigorous examination of the factors that define effective LTACs, as well as effective care for chronic critical illness. Ultimately, these results will provide clinicins, hospital administrators and policy makers with immediate, actionable data about how to use LTACs most effectively and efficiently, leading to improved survival for patients with chronic critical illness.